Liquid crystal display device and liquid crystal orientation method

ABSTRACT

A slit pattern, which is an orientation control element extending in an oblique direction relative to an edge of a pixel electrode on a surface of a TFT substrate, is formed in the pixel electrode to extend in a substantially parallel direction to an extending direction of a bank-shaped pattern. Furthermore, as an orientation control element, fine slit patterns (concave portions in the pixel electrode) are formed locally in a part near the edge of the pixel electrode except in the pixel electrode to extend in an oblique direction relative to an extending direction of the edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 10/047,216, filed Jan. 14,2002.

This application is based upon and claims priority of Japanese PatentApplication No. 2001-029814, filed on Feb. 6, 2001, the contents beingincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to liquid crystal display devices in whicha first substrate having a pixel electrode and an active element and asecond substrate having an opposed electrode have a liquid crystal layerinterposed therebetween with each of the electrodes thereof facing eachother and also relates to liquid crystal orientation methods.

2. Description of the Related Art

Conventionally, a liquid crystal display device in a TN mode in whichliquid crystal material with a positive dielectric anisotropy is put ina dark state and is oriented to be in a horizontal direction relative toa substrate surface and twisted 90° between opposed substrates is widelyused as a liquid crystal display (LCD) using an active matrix.

However, the TN mode has a disadvantage that it is inferior in itsviewing angle characteristic and various studies have been made toimprove the viewing angle characteristic thereof. As a methodsubstituting for the TN mode, an MVA (Multi-domain Vertical Alignment)system in which liquid crystal material with a negative dielectricanisotropy is vertically oriented and liquid crystal molecules undervoltage application are regulated, without giving rubbing treatment tooriented films, to tilt in directions by protrusions and slits which areprovided on surfaces of the substrates has been developed. The MVAsystem has succeeded in improving the viewing angle characteristic to agreat extent.

The structure and function of an MVA system liquid crystal displaydevice will be described below.

The MVA system is a system which performs orientation dividing of avertical orientation type liquid crystal by providing elements in theforms of bank-shaped (linear) protrusions and slits on the substrates.As shown in FIG. 22, FIG. 23A, and FIG. 23B (a sectional view takenalong the line I–I′), the elements 103 in the forms of the linearprotrusions and slits are arranged alternately on an upper substrate 101and a lower substrate 102. Thereby, liquid crystal domains in whichorientation directions on both sides of the element 103 areapproximately 180° different from each other are formed in regionswithout the element 103 (spaced interval parts). In this way, a suitableorientation dividing is realized. This MVA system has improved theviewing angle characteristic of the liquid crystal display device to agreat extent.

Here, the ‘linear (bank-shaped) protrusion’ is made of dielectricmaterial and formed on an electrode (for example, a pixel electrode, anopposed (a common) electrode, and so on) and the ‘slit’ is a concaveportion formed in a part of the electrode. Hereinafter, the sameexpressions in the specification of this patent application designatethe above elements.

However, the conventional MVA system liquid crystal display device has adisadvantage that light transmittance of a panel is lower than that of aliquid crystal display device in a TN mode. One of the reasons will bedescribed with reference to FIGS. 24 and 25.

FIGS. 24A and 24B show states of pixel observation when a conventionalMVA panel used in general is in a white display state. FIGS. 25A and 25Bshow states of liquid crystal orientation.

As shown in FIG. 24A and FIG. 25B, it is seen that a line which appearsdark (a dark line 105) exists in a part of a region near an edge of apixel electrode 104. In this region, as shown in FIG. 24B (a sectionalview taken along the line I–I′) and FIG. 25A, the element 103 on thepixel electrode 104 regulates liquid crystal molecules to tilt in aright direction relative to the element 103 while a slanting electricfield of the edge of the pixel electrode 104 regulates the liquidcrystal molecules to tilt in a left direction. Therefore, liquid crystalorientation directions defined by them are substantially opposite toeach other. As a result, the liquid crystal molecules in this region areoriented in the same direction as a polarizing axial direction, whichoptically causes the dark line to occur and therefore, lowers thetransmittance.

As shown in FIG. 26A and FIG. 26B (a sectional view taken along the lineI–I′), this problem is solvable by applying a method of newly providinga bank-shaped element 106 (an auxiliary bank method) on an opposed partto the edge of the pixel electrode. The newly provided element 106 isdisposed along the edge of the pixel electrode. At this time, theelement 106 regulates the liquid crystal molecules to be oriented in anopposite direction to the direction defined by the slanting electricfield of the edge of the pixel electrode. Thereby, the liquid crystalorientation near the edge of the pixel electrode is caused to besubstantially in the same orientation direction defined by theoriginally provided element 103.

FIGS. 27A and 27B show the position of the dark line within the pixel atthis time.

In FIG. 27A and FIG. 27B, black circles and white circles show singularpoints of an orientation vector and a line connecting the black circlesand the white circles shows the dark line. The dark line whichconventionally enters inside the pixel stays on the newly providedelement 106. Here, the distribution of the singular points and the darklines on the whole pixel is shown in FIG. 28.

In this way, the light transmittance of the panel can be improved byapproximately 10% compared with that in the conventional art. Here, thenewly provided element 106 works in a manner in which it helps theliquid crystal orientation approximate to the original liquid crystalorientation control defined by the originally provided element 103.Therefore, the newly provided element 106 is hereinafter called anauxiliary bank.

However, it is found that a problem of partial unevenness in brightnesswithin the panel, which is recognized as irregular display orununiformity in display brightness, occurs when this method is applied.After investigation, it is found that this problem is caused by thefollowing reason.

In order to drive the liquid crystal molecules, it is necessary to forma TFT element, bus line, and pixel electrode patterns on one of thesubstrates. These patterns are formed by a photolithography process. Atpresent, resist exposure is performed with the surface within the panelbeing divided into regions (exposure by shots using stepper machines) inorder to form fine patterns of approximately several microns at theminimum with the equal shapes and width all over the panel.

At this time, overlapping widths of the substrate and a photomasksometimes deviate a little between adjacent shots from each other. Thisdeviation causes relative position of the edge of the pixel electrodeand the auxiliary bank to vary from shot to shot. As described above,the liquid crystal orientation direction defined by the edge of thepixel electrode and the liquid crystal orientation direction defined bythe auxiliary bank are opposite to each other. Therefore, when therelative position of the edge of the pixel electrode and the auxiliarybank varies, orientation control balance between them varies, whichsometimes influences the liquid crystal orientation near the auxiliarybank. Particularly, when deviation in overlapping width of a TFTsubstrate and an opposed substrate (having the auxiliary bank) is large,this problem occurs distinctly.

A difference in states of the liquid crystal orientation (the dark line)caused by the variation of the relative position of the auxiliary bankand the edge of the pixel electrode is shown in FIGS. 29A and 29B. Whenthe overlapping width of the auxiliary bank and the edge of the pixelelectrode is wide (FIG. 29A), the dark line stays on the auxiliary bank.Meanwhile, when the overlapping width is narrow (FIG. 29B), the darkline gets inside the pixel. As a result, a difference in transmittancebetween both of the pixels is caused. In this way, brightness among eachshot is caused to be different from each other, which is recognized asirregular display or ununiformity in display brightness.

As a countermeasure for improving this problem, it can be thought ofthat the auxiliary bank is disposed further inside the edge of the pixelelectrode than in the conventional art so that the effect of theauxiliary bank does not vary even with some degree of overlappingdeviation. However, in this case, it is found that a dark region newlyoccurs as shown in FIG. 30 and the light transmittance of the panel islowered.

So far, since the auxiliary bank and the bank on the pixel electrode areformed under the same condition, they also give the same influence tothe orientation of the liquid crystal molecules. The bank on the pixelelectrode regulates the liquid crystal molecules in the bank spacedinterval part to tilt in a perpendicular direction relative to anextending direction of the bank. Here, when the auxiliary bank getssufficiently inside the pixel electrode, the liquid crystal molecules inits vicinity also tilt in a perpendicular direction relative to anextending direction of the bank (half-tone dot meshing parts in FIG.28). Since this direction is substantially equal to the polarizing axialdirection of a polarizing plate, the light transmittance of the panel islowered.

Furthermore, it is proposed that the auxiliary bank is made lower inheight than the bank on the pixel electrode. However, this necessitatesbanks different in height to be formed on the same substrate andconsequently a process becomes complicated.

From FIGS. 26A and 26B, and FIG. 28, it is apparent that ideally, theliquid crystal orientation near the auxiliary bank is in a direction of45° relative to the auxiliary bank and in the perpendicular directionrelative to the bank on the pixel electrode and the dark line stays onthe auxiliary bank and does not get inside the pixel electrode. However,in the present structure, the various problems as described above occurand it is very difficult to stably realize the ideal orientation state.

As described above, when the MVA system is applied, the viewing anglecharacteristic is greatly improved. On the contrary, the slantingelectric field which occurs near the edge of the pixel electrode has abig influence and promotes a so-called dark lines or a part of schlierenpattern to be formed. Even when the auxiliary bank is provided in orderto cope with this problem, the influence by the deviation in maskoverlapping at the time of patterning sometimes arises, and therefore,it is difficult to obtain an even liquid crystal orientation state.

SUMMARY OF THE INVENTION

It is an object of the present invention to prevent an occurrence ofirregular display or ununiformity in display brightness and greatlyimprove light transmittance of a panel and thereby realize a liquidcrystal display device with high reliability by suppressing orientationabnormality within a pixel region for display which is caused by aslanting electric field occurring inside the pixel region for displayand in its vicinity and controlling liquid crystal orientation in astable and ideal state.

The present invention relates to a liquid crystal display device inwhich a first substrate having a pixel electrode and an active elementand a second substrate having an opposed electrode, which have a liquidcrystal layer interposed therebetween with each of the electrodesthereof facing each other.

A liquid crystal display device according to the first aspect of thepresent invention is characterized in that when a direction of anorientation regulating force given to liquid crystal molecules of theliquid crystal layer within a region of the pixel electrode is taken asa first direction and a direction of an orientation regulating force dueto an edge of the pixel electrode on the first substrate given to theliquid crystal molecules near the edge is taken as a second direction,an orientation control element giving an orientation regulating force ina third direction which counteracts the orientation regulation force inthe second direction is locally provided in a part near the edge.

A liquid crystal display device according to the second aspect of thepresent invention is characterized in that an orientation controlelement giving an orientation regulating force to the liquid crystalmolecules near the edge of the pixel electrode on the first substrate islocally provided near the edge of the pixel electrode on the firstsubstrate so that the liquid crystal molecules including those near theedge are oriented in substantially the same direction when voltage isbeing applied between the pixel electrode and the opposed electrode.

Specifically, in the first and second aspects, it is appropriate thatthe orientation control element is constituted by a plurality of fineslits formed in the pixel electrode in an oblique direction relative toan extending direction of the edge.

It is also appropriate that the orientation control element isconstituted by a plurality of fine protrusions formed on the pixelelectrode in the oblique direction relative to the extending directionof the edge.

In this case, at least a part of the fine slits or the fine protrusionsare preferably formed to have different shapes and/or spaced intervalsand/or length of arrangement from others.

In the first and second aspects, each of the corresponding orientationcontrol elements is formed near the edge of the pixel electrode on thefirst substrate on which the pixel electrode is also formed. This makesit possible to almost completely eliminate an adverse effect ofdeviation in pasting width of the two substrates and greatly widen amanufacturing margin and sufficiently cope with an abrupt disorder ofmanufacturing apparatuses.

A liquid crystal display device according to the third aspect of thepresent invention is characterized in that a first orientation controlelement extending in a nonparallel direction relative to the extendingdirection of the edge of the pixel electrode and a second orientationcontrol element extending in a parallel direction relative to theextending direction of the edge are provided on at least one of thefirst substrate and the second substrate, and the first orientationcontrol element has a wider width than the second orientation controlelement.

A liquid crystal display device according to the fourth aspect of thepresent invention is characterized in that a first orientation controlelement extending in the non-perpendicular direction and the nonparalleldirection relative to the extending direction of the edge of the pixelelectrode and a second orientation control element extending in theparallel direction relative to the extending direction of the edge areprovided on at least one of the first substrate and the secondsubstrate, and the liquid crystal molecules of the liquid crystal layeron the second orientation control element are oriented in a non-verticaldirection relative to the substrate when no voltage is being appliedbetween the pixel electrode and the opposed electrode.

A liquid crystal display device according to the fifth aspect of thepresent invention is characterized in that a first orientation controlelement extending in the non-perpendicular direction and the nonparalleldirection relative to the extending direction of the edge of the pixelelectrode and a second orientation control element extending in theparallel direction relative to the extending direction of the edge areprovided on at least one of the first substrate and the secondsubstrate, and at least a part of the liquid crystal molecules of theliquid crystal layer on the second orientation control element areoriented in a vertical direction relative to the substrate when voltageis being applied between the pixel electrode and the opposed electrode.

A liquid crystal display device according to the sixth aspect of thepresent invention is characterized in that a first orientation controlelement extending in the non-perpendicular direction and the nonparalleldirection relative to the extending direction of the edge of the pixelelectrode and a second orientation control element extending in theparallel direction relative to the extending direction of the edge areprovided on at least one of the first substrate and the secondsubstrate, and the second orientation control element is composed of anassembly of shapes having directivity in a direction of a substrate'splane surface.

Specifically, in the third to the sixth aspects, it is appropriate thatthe first orientation control element and/or the second orientationcontrol element is constituted by slits or protrusions formed on thepixel electrode or the opposed electrode.

In the third aspect, the first orientation control element is wider inwidth than the second orientation control element so that the strengthof orientation control defined by the second orientation control elementbecomes weaker than an orientation control force defined by the firstorientation control element on the pixel electrode. This makes itpossible to stably realize an ideal state in which the liquid crystalmolecules are oriented in a direction of approximately 45° relative tothe second orientation control element and in a perpendicular directionrelative to the first orientation control element on the pixelelectrode.

In the fourth aspect, when no voltage is being applied, the liquidcrystal molecules on the second orientation control element isnon-vertically oriented and is oriented in the same direction as theorientation direction of the liquid crystal molecules which causes adark line to occur under voltage application, that is, a paralleldirection to an extending direction of the second orientation controlelement. Consequently, when voltage is being applied, the dark lineoccurs stably only on the second orientation control element, theorientation on which is made to be non-vertical in advance.

In the fifth aspect, the liquid crystal molecules on the secondorientation control element are in vertical orientation under voltageapplication. One of the causes for strengthening the slanting (oblique)electric field of the pixel electrode, which is one of the factorscausing unevenness among each shot at the time of patterning, is aninfluence of an electric field of an adjacent bus line. In this aspect,a region in which the liquid crystal orientation does not change(remains in the vertical orientation) is provided between the bus lineand the pixel electrode. This makes it possible to eliminate theinfluence given to the liquid crystal orientation on the pixel electrodeby the bus line. Therefore, the slanting electric field of the edge ofthe pixel electrode can be weakened and the unevenness among each shotis prevented from occurring.

In the sixth aspect, the structure having directivity is provided as thesecond orientation control element. The directivity is in the samedirection as the orientation direction of the liquid crystal moleculeswhich causes the dark line to occur under voltage application, that is,a parallel direction to the extending direction of the secondorientation control element. Thereby, the dark line occurs stably onlyon the second orientation control element having the directivity undervoltage application. This makes it possible to eliminate the adverseeffect caused by the occurrence of the dark line at the inside but onlyat the edge and realize an actually high light transmittance of thepanel.

The present invention also relates to a liquid crystal orientationmethod of a liquid crystal layer in the liquid crystal display device.According to the method, the liquid crystal molecules are oriented inaccordance with the first to the sixth aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically showing the structure of aliquid crystal display device according to the present invention;

FIGS. 2A to 2C show states near a pixel of a liquid crystal displaydevice according to the first embodiment of the present invention;

FIGS. 3A to 3C show states when orientation regulating forces are givento liquid crystal molecules in first to third directions;

FIG. 4 is a plane view showing a state near a pixel of a liquid crystaldisplay device according to the second embodiment of the presentinvention;

FIG. 5 is a graph showing a transmittance-voltage (T-V) characteristicof the liquid crystal display device according to the second embodiment;

FIGS. 6A to 6F are micrographs showing liquid crystal orientationstates;

FIG. 7 shows micrographs of liquid crystal orientation states;

FIG. 8 is a plane view showing a state near a pixel in modification 1 ofthe liquid crystal display device according to the second embodiment;

FIG. 9 is a plane view showing a state near a pixel in modification 2 ofthe liquid crystal display device according to the second embodiment;

FIG. 10 is a plane view showing a state near a pixel in modification 3of the liquid crystal display device according to the second embodiment;

FIG. 11 shows various effects and features in the first and secondembodiments and comparative examples thereof;

FIG. 12 shows various effects and features in the first and secondembodiments and comparative examples thereof;

FIG. 13 is a plane view showing a state near a pixel of a liquid crystaldisplay device according to the third embodiment of the presentinvention;

FIGS. 14A and 14B are schematic views showing states near a pixel in aliquid crystal display device according to the fourth embodiment of thepresent invention;

FIGS. 15A and 15B show states of liquid crystal orientation;

FIGS. 16A and 16B are schematic views showing states near a pixel in amodification of the liquid crystal display device according to thefourth embodiment;

FIGS. 17A and 17B are schematic views showing states of liquid crystalorientation;

FIGS. 18A and 18B are schematic views showing states near a pixel in aliquid crystal display device according to the fifth embodiment of thepresent invention;

FIGS. 19A and 19B are schematic views showing states near a pixel in aliquid crystal display device according to the sixth embodiment of thepresent invention;

FIGS. 20A and 20B are schematic views showing states near a pixel inanother example of the liquid crystal display device according to thesixth embodiment;

FIGS. 21A and 21B are schematic views showing states near a pixel in aliquid crystal display device according to the seventh embodiment of thepresent invention;

FIG. 22 is a plane view showing a state near a pixel in a conventionalliquid crystal display device according to an MVA system;

FIGS. 23A and 23B are sectional views showing states when a bank-shapedpattern is provided in a conventional liquid crystal display device;

FIGS. 24A and 24B show states when the bank-shaped pattern is providedin the conventional liquid crystal display device;

FIGS. 25A and 25B are schematic views showing liquid crystalorientation;

FIGS. 26A and 26B are sectional views showing states when thebank-shaped pattern and an auxiliary bank are provided in theconventional liquid crystal display device;

FIGS. 27A and 27B are plane views showing states near the pixel in theconventional liquid crystal display device according to the MVA system;

FIG. 28 is a plane view showing distribution of singular points and darklines on a whole pixel;

FIGS. 29A and 29B are plane views showing overlapping states of theauxiliary bank and a pixel edge; and

FIG. 30 is a plane view showing an overlapping state of the auxiliarybank and the pixel edge.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to drawings.

First Embodiment

FIG. 1 is a schematic sectional view showing a main structure of aliquid crystal display device according to the first embodiment of thepresent invention.

The liquid crystal display device, which is based on a so-called MVAsystem, is composed of a pair of transparent glass substrates 11, 12facing each other with a predetermined spaced interval being providedtherebetween and a liquid crystal layer 13 interposed between thetransparent glass substrates 11, 12.

On one of the transparent glass substrates 11, pixel electrodes 15 andnot-shown thin film transistors (TFT), which are formed by a thin filmsemiconductor technique using a thin semiconductor film such as anamorphous silicon film or a polycrystalline silicon film and work asactive elements, are formed with an insulating layer 14 being providedbetween them and the substrate 11. A transparent oriented film 16 a isformed to cover the pixel electrodes 15. On the other transparent glasssubstrate 12, a color filter 17, a common electrode (an opposedelectrode) 18, and an oriented film 16 b are laminated in sequencegenerally. The glass substrates 11, 12 are fixed in a manner in whichthe oriented films 16 a, 16 b are pressed against each other to hold theliquid crystal layer 13 therebetween. Outside the substrates 11, 12,polarizers 19, 20 are provided respectively. The pixel electrodes 15 areformed with active matrixes (TFT matrixes) and, in the example in FIG.1, data bus lines 21 to which drain electrodes of the TFTs are connectedare shown. Moreover, gate bus lines, though not shown, to which gateelectrodes of the TFTs are connected are also formed.

As shown in FIG. 2A, on a surface of the transparent glass substrate 12as a CF substrate, a bank-shaped pattern 22, which is an orientationcontrol element extending in an oblique direction relative to an edge ofthe pixel electrode 15 on the opposed transparent glass substrate 11, isformed on the common electrode (under the oriented film). Thereby,predetermined division, for example, four divided orientation, isperformed to each pixel of the liquid crystal layer 13.

Meanwhile, as shown in FIG. 2A and FIG. 2B, on a surface of thetransparent glass substrate 11 as a TFT substrate, a slit pattern 23,which is an orientation control element extending in the obliquedirection in this case relative to the edge of the pixel electrode 15,is formed in the pixel electrode 15 to extend in a substantiallyparallel direction to an extending direction of the bank-shaped pattern22. Furthermore, a hollow 24 is locally formed as an orientation controlelement in a part other than the pixel electrode 15 in the vicinity ofthe edge of the pixel electrode 15.

When an auxiliary bank is formed on the CF substrate as in aconventional art, a margin for pasting the substrates is onlyapproximately ±3 μm. This gives only a minimum margin even when apasting apparatus for substrates with high precision is utilized andenables manufacturing only when perfect control of process conditions isrealized. Therefore, there is always a risk that a large amount ofunevenness among each shot may occur to a panel even when amanufacturing apparatus gets into a bad condition only a little. Thisproblem is basically caused because the auxiliary bank for controllingthe orientation of a pixel electrode edge portion is not provided on apixel electrode side but on an opposed substrate side. According to thisembodiment, the hollow 24 as the orientation control element of the edgeof the pixel electrode 15 is provided in the transparent glass substrate11 on which the pixel electrode 15 is formed so that almost no influenceis given by deviation in pasting.

Therefore, according to this embodiment, it is possible to provide aliquid crystal display device which is capable of realizing highcontrast by utilizing the MVA system, securing high reliability byrealizing an excellent viewing characteristic, and achieving moreuniform distribution of brightness. At the same time, a liquid crystaldisplay device is provided which is capable of greatly widening amanufacturing margin and sufficiently coping with an abrupt disorder ofthe manufacturing apparatus.

As described above, to form the hollow 24 as the orientation controlelement of the edge on the surface of the transparent glass substrate 11on which the pixel electrode 15 is formed means, in other words, toprovide in a part of a pixel region for display near the edge anorientation control factor which gives an orientation disturbing forcein a third direction different from a first direction of a liquidcrystal orientation regulating force given by the bank-shaped pattern 22and the slit pattern 23 within the pixel region for display and a seconddirection of a liquid crystal orientation regulating force given by aslanting electric field occurring near the edge of the pixel electrode.As a result, the manufacturing margin is increased.

A principle of providing the orientation control factor is shown inFIGS. 3A to 3C in general.

Conventionally, a dark line occurs due to orientation abnormality nearthe edge of the pixel electrode (FIG. 3A). But, in contrast, theinfluence of the orientation abnormality due to the slanting electricfield is eliminated by giving to liquid crystal molecules theorientation regulating force in the third direction (FIG. 3B) whichmakes a bigger angle φ2 with the second direction than an angle φ1 madeby the first and second directions (FIG. 3C). The angle φ1 and the angleφ2 can be equal.

[Specific Example of Structure]

As shown in FIGS. 2A to 2C, the hollow 24 is formed in a part near theedge of the pixel electrode (corresponding to a part where theconventional auxiliary bank is formed). The hollow 24 is formed to beapproximately 0.5 μm in depth by patterning a SiN insulating film on theside of the transparent glass substrate 11 as the TFT substrate. Theliquid crystal molecules at the edge of the pixel electrode have apretilt angle in an opposite direction to the direction of the electricfield, being influenced by the hollow 24. This prevents the dark linefrom occurring as in a conventional case in which the auxiliary bank isprovided.

As explained above, according to this embodiment, the orientationabnormality within the pixel region for display caused by the slantingelectric field which occurs near the pixel edge and in its vicinity issuppressed and the liquid crystal orientation is controlled to be in astable and ideal state. Thereby, irregular display or ununiformity indisplay brightness is prevented from occurring and the lighttransmittance of the panel is greatly improved. This makes it possibleto realize a liquid crystal display device with high reliability.

Incidentally, instead of the orientation control element, or preferably,in addition to the orientation control element, a Cs electrode may beprovided along the edge of the pixel electrode. The Cs electrode has thesame electric potential as that of the opposed substrate side so thatliquid crystal molecules in the part where the Cs electrode is provideddo not tilt. Therefore, providing the Cs electrode makes it possible toshield the influence of the electric field from the bus line (electricfield intensity does not easily fluctuate near the edge of the pixelelectrode) so that stable orientation can be constantly obtained.

Second Embodiment

The second embodiment of the present invention will be described below.Here, a liquid crystal display device based on the MVA system will bedescribed like in the first embodiment. But the orientation controlelement formed near the pixel electrode 15 on the TFT substrate side hasa different form.

Like in the first embodiment schematically shown in FIG. 1, this liquidcrystal display device is composed of a pair of transparent glasssubstrates 11, 12 facing each other with a predetermined spaced intervalbeing provided therebetween and the liquid crystal layer 13 interposedbetween the transparent glass substrates 11, 12. On the transparentglass substrate 11, the pixel electrodes 15, data bus lines 21, a gatebus line (not shown), and so on are formed. On the transparent glasssubstrate 12, the color filter 17, the common electrode 18, and so onare formed.

In the liquid crystal display device, as shown in FIG. 4, thebank-shaped pattern 22, which is the orientation control elementextending in an oblique direction relative to the edge of the pixelelectrode 15 on the opposed transparent glass substrate 11, is formed onthe surface of the transparent glass substrate 12 as the CF substrate.Thereby, predetermined division, for example, the four dividedorientation, is performed on each pixel of the liquid crystal layer 13.

Meanwhile, on the surface of the transparent glass substrate 11 as theTFT substrate, the slit pattern 23, which is the orientation controlelement extending in the oblique direction relative to the edge of thepixel electrode 15, is formed on the pixel electrode 15 to extendsubstantially in parallel to an extending direction of the bank-shapedpattern 22. Furthermore, near the edge of the pixel electrode 15, fineslit patterns 25 (concave portions in the pixel electrode 15) are formedlocally in an oblique direction relative to the extending direction ofthe edge (for example, 45°) to constitute an orientation controlelement.

According to this embodiment, forming in the pixel electrode 15 the fineslit patterns 25 as the orientation control element of the edge of thepixel electrode 15 makes it possible to eliminate almost all theinfluences by deviation in pasting.

Therefore, according to this embodiment, it is possible to provide aliquid crystal display device which is capable of realizing highcontrast by utilizing the MVA system and securing high reliability byrealizing an excellent viewing characteristic. At the same time, aliquid crystal display device is provided which is capable of wideningthe manufacturing margin to a great extent and, sufficiently coping withthe abrupt disorder of the manufacturing apparatus.

A transmittance-voltage characteristic (a T-V characteristic) when thisembodiment is actually applied is shown in FIG. 5 and FIGS. 6A to 6F. Itis apparent that the orientation near the edge of the pixel electrode ismade in good order by the fine slit patterns 25 without the conventionalauxiliary bank being provided. With sufficient voltage being applied,the effect of the fine slit patterns 25 fully works to improve thetransmittance to the same level as that when the auxiliary bank isprovided.

[Specific Example of Structure]

As shown in FIG. 4, cuts of the fine slit patterns 25 are formed in thepixel electrode 15 near the edge of the pixel electrode. It has beenfound that forming the fine slit patterns 25 causes the liquid crystalmolecules to tilt in a parallel direction to an extending direction ofthe fine slit patterns 25 under voltage application. This effect isutilized near the edge. It is apparent from FIGS. 6A to 6F that thediorder of the liquid crystal orientation is suppressed near the edge.

FIG. 7 shows a difference in states of the orientation depending on thedepth of the cuts of the fine slit patterns 25. In utilizing the fineslit patterns 25, more effect is obtained when the slit depth of thepatterns is made sufficiently long.

Moreover, according to this embodiment, since the liquid crystalorientation near the edge is made in good order by cleverly planningdistribution of the electric field, not much effect is obtained at lowvoltage but as the higher voltage is applied, the more effect isobtained. As shown in FIG. 5, display chromaticity of a panel with theauxiliary bank becomes white at applied voltage of 5.3V while that of apanel without the auxiliary bank becomes white at applied voltage of6.3V. With sufficient voltage being applied, the transmittance equal toor higher than that when the auxiliary bank is utilized is obtained. Inthis embodiment, the fine slit patterns 25 are also formed by patterninga part of the pixel electrode 15 so that no influence by the deviationin pasting of the two substrates is given to the relative positionbetween the pixel electrode and the edge and therefore, great increasein a pasting margin is realized.

As explained above, according to this embodiment, the orientationabnormality within the pixel region for display, which is caused by theslanting electric field occurring outside the pixel region for displayand in its vicinity, is further suppressed and the liquid crystalorientation is controlled to be in a stable and ideal state. As aresult, irregular display or ununiformity in display brightness isprevented from occurring and the light transmittance of the panel andbrightness uniformity are greatly enhanced. This makes it possible torealize a liquid crystal display device with high reliability.

Modifications

Modifications of the second embodiment will be described below.

In the modifications, at least a part of the fine slit patterns 25 inthe liquid crystal display device according to the second embodiment areformed to have different shapes and/or be arranged at different spacedintervals. Modifications 1 to 3 will be described below in order asspecific examples.

(Modification 1)

Here, as shown in FIG. 8, each of the fine slit patterns 25 is differentin length from each other and the orientation regulating force in thethird direction is adjusted freely. Incidentally, each of the fine slitpatterns 25 is also different in length in the example shown in FIG. 4.In this case, however, they are formed to match the form of the pixelelectrode 15 near the edge. Meanwhile, in this example, the length ofeach of the slit patterns 25 is defined independently from the shape ofthe pixel electrode 15 near the edge.

(Modification 2)

Here, as shown in FIG. 9, each of the fine slit patterns 25 is differentfrom each other in length, width, and a spaced interval between adjacentfine slit patterns 25. Consequently, the orientation regulating force inthe third direction can be adjusted more delicately at a desiredstrength.

(Modification 3)

Here, as shown in FIG. 10, each of the fine slit patterns 25 has atapered shape to have directivity. This makes it possible to stronglydetermine a tilting direction defined by the orientation regulatingforce in the third direction.

The first and second embodiments have been described above. Variouseffects and features of the examples and comparative examples ofstructure are summarized in FIG. 11 and FIG. 12.

Note that {circle around (1)} shows the conventional structure with theauxiliary bank being provided on the CF substrate, {circle around (2)}the conventional structure without the auxiliary bank, {circle around(3)} the structure with the auxiliary bank being provided to extend in adifferent direction, {circle around (4)} the structure with the hollow24 in the first embodiment being provided, and {circle around (5)} thestructure with the fine slit patterns 25 in the second embodiment beingprovided, respectively.

As is apparent from the drawings, the liquid crystal display deviceshaving the structures in the first and second embodiments are capable ofrealizing high transmittance and securing a misalignment margin withoutsacrificing the transmittance, which is not realized in the comparativeexamples. Particularly, the structure in the second embodiment shows themost distinguished effect.

Third Embodiment

The third embodiment of the present invention will be described below.Here, a liquid crystal display device based on the MVA system like inthe second embodiment will be described. But, an orientation controlelement provided near the edge of the pixel electrode is different fromthat in the second embodiment.

In the liquid crystal display device according to this embodiment, asshown in FIG. 13, on the surface of the transparent glass substrate 11as the TFT substrate, the slit pattern 23, which is the orientationcontrol element extending in the oblique direction relative to the edgeof the pixel electrode 15 (indicated by the arrow A), is formed in thepixel electrode 15 to extend substantially in parallel to the extendingdirection of the bank-shaped pattern 22 on the transparent glasssubstrate 12. Furthermore, near the edge of the pixel electrode 15, finelinear protrusion patterns 26 are formed locally as an orientationcontrol element in the oblique direction relative to the extendingdirection of the edge (for example, 45°).

According to this embodiment, forming the fine protrusion patterns 26,which constitute an orientation control element of the edge of the pixelelectrode 15, on the pixel electrode 15 makes it possible to eliminatealmost all the influence of the deviation in pasting.

Therefore, according to this embodiment, it is possible to provide aliquid crystal display device which is capable of realizing highcontrast by utilizing the MVA system and securing high reliability byrealizing an excellent viewing characteristic. At the same time, aliquid crystal display device is provided which is capable of widening amanufacturing margin to a greater extent than in the first embodimentand sufficiently coping with an abrupt disorder of the manufacturingapparatus.

Incidentally, it is also appropriate in this embodiment like in themodification examples of the second embodiment that each of the fineprotrusion patterns 26 is made different in length, width, and spacedintervals from adjacent fine protrusion patterns 26 so that theorientation regulating force in the third direction is adjusteddelicately at a desired strength.

Fourth Embodiment

The fourth embodiment of the present invention will be described below.Here, a liquid crystal display device based on the MVA system like inthe first embodiment will be described. But, an orientation controlelement provided near the edge of the pixel electrode is different.

Like in the first embodiment schematically shown in FIG. 1, this liquidcrystal display device is composed of a pair of transparent glasssubstrates 11, 12 facing each other with a predetermined spaced intervalbeing provided therebetween and the liquid crystal layer 13 interposedbetween the transparent glass substrates 11, 12. On the transparentglass substrate 11, the pixel electrodes 15, the data bus lines 21, thegate bus line (not shown), and so on are formed. On the transparentglass substrate 12, the color filter 17, the common electrode 18, and soon are formed.

In the liquid crystal display device, as shown in FIG. 14A, on thesurface of the transparent glass substrate 11 as the TFT substrate, theslit pattern 23, which is the orientation control element extending inthe oblique direction relative to the edge of the pixel electrode 15, isformed in the pixel electrode 15.

Meanwhile, on the surface of the transparent glass substrate 12 as theCF substrate, a slit pattern 31, which is an orientation control elementextending in the oblique direction relative to the edge of the pixelelectrode 15 on the opposed transparent glass substrate 11, is formed inthe common electrode to extend substantially in parallel to theextending direction of the slit pattern 23. Thereby, predetermineddivision is performed on each pixel of the liquid crystal layer 13. Forexample, the four divided orientation is performed when parts of pixelare arranged in one pixel, as in FIG. 22.

Moreover, on the surface of the transparent glass substrate 12, a slitpattern 32 is integrally formed with the slit pattern 31 along the edgeof the pixel electrode 15 to branch off in an oblique direction from theslit pattern 31 as shown in FIG. 14A and FIG. 14B (sectional views takenalong the I–I′ line and II–II′ line). The slit pattern 32 is formed tobe smaller in width than the slit pattern 31.

As a result, an orientation control defined by the slit pattern 32 isweaker in strength than the orientation control defined by the slitpattern 23 in the pixel electrode 15 as shown in FIG. 15A and FIG. 15B.At this time, the liquid crystal orientation defined by the slit pattern32 is oriented to deviate from a perpendicular direction relative to theextending direction of the slit pattern 23. In this way, an ideal statein which the liquid crystal molecules are oriented in the direction ofapproximately 45° relative to the slit pattern 32 and in theperpendicular direction relative to the slit pattern 23 in the pixelelectrode 15 is stably realized.

[Specific Example of Structure]

As shown in FIGS. 14A and 14B, the slit pattern 23 for controlling theliquid crystal orientation is formed in the pixel electrode 15 on thetransparent glass substrate (the TFT substrate) 11 having the pixelelectrodes, the active element (TFT), the data bus lines, the gate busline, and so on. On the transparent glass substrate (the CF substrate)12 having the common electrode and so on, the slit pattern 31 forcontrolling the liquid crystal orientation and the slit pattern 32 forauxiliary control provided along the edge of the pixel electrode areformed in the common electrode. The slit pattern 32 on the CF substrateis smaller in width than the slit pattern 31 which is arranged to extendin a nonparallel direction and in a non-vertical direction relative tothe edge.

A TFT substrate with a 15-inch type screen and a pixel number of1024×768 (XGA) is utilized. A pixel pitch is 297 μm. The slit pattern 23on the TFT substrate is formed to extend in the direction ofapproximately 45° relative to the edge of the pixel electrode. The slitwidth thereof is 10 μm. As for the slit patterns on the CF substrate,the slit pattern 31 is formed to extend in the direction of 45° relativeto the edge of the pixel electrode and the slit pattern 32 is formedalong the edge of the pixel electrode. The slit pattern 31 is 10 μm inwidth and the slit pattern 32 is 5 μm in width. An overlapping margin ofthe slit pattern 32 and the pixel electrode is 5 μm.

Oriented films are formed and coated over the surfaces of the substratesthus fabricated. Here, the substrates are spin-coated with oriented filmmaterial thereon, pre-baked at 80° C. for one minute (using a hotplate),and thereafter, subjected to permanent baking at 180° C. for 60 minutes(using a clean oven). The substrates on which the oriented films areformed in this way are pasted with each other in a manner in which theslit patterns deviate from each other by a half pitch to fabricate anempty cell. A cell gap is 4 μm and a distance of each spaced intervalpart between each slit pattern is 25 μm. To the empty cell thusfabricated, liquid crystal material is injected and after variousprocesses the liquid crystal display device is completed.

As explained above, according to this embodiment, the orientationabnormality within the pixel region for display caused by the slantingelectric field which occurs outside the pixel region for display and inits vicinity is suppressed and the liquid crystal orientation iscontrolled to be in a stable and ideal state. Thereby, irregular displayor ununiformity in display brightness is prevented from occurring andthe light transmittance of the panel is greatly improved. This makes itpossible to realize a liquid crystal display device with highreliability.

Modification

A modification of the fourth embodiment will be described below.

In this modification, bank-shaped patterns instead of the slit patternsare formed as orientation control elements on the CF substrate in theliquid crystal display device according to the fourth embodiment.

In the liquid crystal display device, as shown in FIG. 16A, the slitpattern 23, which is the orientation control element extending in theoblique direction relative to the edge of the pixel electrode 15, isformed in the pixel electrode 15 on the surface of the transparent glasssubstrate 11 as the TFT substrate.

Incidentally, in this case, a bank-shaped pattern, which is a linearprotrusion, may be formed instead of the slit pattern 23 in the sameposition where the slit pattern 23 is formed.

Meanwhile, on the surface of the transparent glass substrate 12 as theCF substrate, a bank-shaped (linear protrusion) pattern 41, which is anorientation control element extending in the oblique direction relativeto the edge of the pixel electrode 15 on the opposed transparent glasssubstrate 11, is formed on the common electrode to extend substantiallyin parallel to the extending direction of the slit pattern 23.Consequently, predetermined division, for example, the four dividedorientation, is performed on each pixel of the liquid crystal layer 13.

Moreover, on the surface of the transparent glass substrate 12, abank-shaped pattern 42 is integrally formed with the bank-shaped pattern41 along the edge of the pixel electrode 15 to branch off in an obliquedirection from the bank-shaped pattern 41 as shown in FIG. 16A and FIG.16B (sectional views taken along the I–I′ line and II–II′ line). Thebank-shaped pattern 42 is formed to be smaller in width than thebank-shaped pattern 41.

As a result, orientation control defined by the bank-shaped pattern 42is weaker in strength than the orientation control defined by the slitpattern 23 in the pixel electrode 15 as shown in FIG. 17A and FIG. 17B.At this time, the liquid crystal orientation defined by the bank-shapedpattern 42 is oriented to deviate from a perpendicular directionrelative to the extending direction of the slit pattern 23. Thus, anideal state in which the liquid crystal molecules are oriented in thedirection of approximately 45° relative to the bank-shaped pattern 42and in the perpendicular direction relative to the slit pattern 23 inthe pixel electrode 15 can be stably realized.

[Specific Example of Structure]

The structure of this example is the same as the specific structure inthe fourth embodiment except in the following point.

As shown in FIGS. 16A and 16B, the bank-shaped patterns are formed onthe CF substrate side. Two types of the bank-shaped patterns areprovided. One of them extends in the direction of 45° relative to theedge of the pixel electrode 15 (the bank-shaped pattern 41) and theother one extends along the edge of the pixel electrode 15 (thebank-shaped pattern 42). They are different in width. The bank-shapedpattern 41 is 10 μm in width and the bank-shaped pattern 42 is 3 μm inwidth. An overlapping width of the bank-shaped pattern 42 and the pixelelectrode 15 is 5 μm.

A photosensitive acrylic resin PC-335 (manufactured by JSR) is used formaterial for the bank-shaped patterns. The bank-shaped patterns areformed in a manner in which the substrate is spin-coated with the resinthereon, baked at 90° C. for 20 minutes (using a clean oven),selectively irradiated with ultraviolet rays using a photomask,developed with an organic alkali type developing solution (TMAHO 0.2 wt% aqueous solution), and baked at 200° C. for 60 minutes (using theclean oven). The CF substrate on which the bank-shaped patterns areformed is subjected to ashing treatment, and thereafter, a verticallyoriented film is coated thereon. The ashing treatment is performed in anoxygen plasma atmosphere with electric power of 500 W being applied forapproximately one minute.

As explained above, according to this modification, the orientationabnormality within the pixel region for display caused by the slantingelectric field which occurs outside the pixel region for display and inits vicinity is suppressed and the liquid crystal orientation iscontrolled to be in a stable and ideal state. Consequently, irregulardisplay or ununiformity in display brightness is prevented fromoccurring and the light transmittance of the panel is greatly enhanced.This makes it possible to realize a liquid crystal display device withhigh reliability.

Note that characteristics of the fourth embodiment and its modificationexample are that the orientation control elements are changed in theirwidths and shapes. Therefore, other conditions such as the overlappingwidth with the edge of the pixel electrode 15 is not restrictive of thepresent invention.

Fifth Embodiment

The fifth embodiment of the present invention will be described below.Here, a liquid crystal display device based on the MVA system like inthe fourth embodiment will be described. But, an orientation controlgiven near the edge of the pixel electrode is performed in a differentway.

Like in the first embodiment schematically shown in FIG. 1, this liquidcrystal display device is composed of a pair of transparent glasssubstrates 11, 12 facing each other with a predetermined spaced intervalbeing provided therebetween and the liquid crystal layer 13 interposedbetween the transparent glass substrates 11, 12. On the transparentglass substrate 11, the pixel electrode 15, the data bus lines 21, thegate bus line (not shown), and so on are formed. On the transparentglass substrate 12, the color filter 17, the common electrode 18, and soon are formed.

In the liquid crystal display device, as shown in FIG. 18A, the slitpattern 23, which is the orientation control element extending in theoblique direction relative to the edge of the pixel electrode 15, isformed in the pixel electrode 15 on the surface of the transparent glasssubstrate 11 as the TFT substrate.

Incidentally, in this case, a bank-shaped pattern, which is a linearprotrusion, may be formed instead of the slit pattern 23 in the sameposition where the slit pattern 23 is formed.

Meanwhile, on the surface of the transparent glass substrate 12 as theCF substrate, the bank-shaped (linear protrusion) pattern 41, which isthe orientation control element extending in the oblique directionrelative to the edge of the pixel electrode 15 on the opposedtransparent glass substrate 11, is formed on the common electrode toextend substantially in parallel to the slit pattern 23. Thereby,predetermined division, for example, the four divided orientation, isperformed on each pixel of the liquid crystal layer 13.

Moreover, on the surface of the transparent glass substrate 12, thebank-shaped pattern (an auxiliary bank) 42 is integrally formed with thebank-shaped pattern 41 along the edge of the pixel electrode 15 tobranch off in the oblique direction from the bank-shaped pattern 41 asshown in FIG. 18A and FIG. 18B (sectional views taken along the I–I′line and the II–II′ line). The liquid crystal molecules of the liquidcrystal layer 13 on the bank-shaped pattern 42 are non-verticallyoriented when no voltage is being applied between the pixel electrode 15of the TFT substrate and the common electrode 18 of the CF substrate.

Incidentally, in this case, slit patterns, which are linear protrusions,may be provided instead of the bank-shaped patterns 41, 42 in the samepositions where the bank-shaped patterns 41, 42 are formed.

Here, the liquid crystal orientation direction is the same as anorientation direction of the liquid crystal molecules which causes thedark line to occur under voltage application, that is, a paralleldirection to the extending direction of the bank-shaped pattern 42.Thus, the dark line occurs stably only on the bank-shaped pattern 42 onwhich the liquid crystal molecules are non-vertically oriented inadvance. Consequently, an actual adverse effect due to an occurrence ofthe dark line is eliminated.

(Specific Example of Structure)

The structure of this example is the same as the specific structure inthe fourth embodiment except in the following point.

As shown in FIGS. 18A and 18B, the liquid crystal molecules on thebank-shaped pattern 42 disposed along the edge of the pixel electrode 15are non-vertically oriented. The non-vertical orientation is realized byrepelling the oriented film coated on the bank-shaped pattern 42 withthe ashing treatment not being applied selectively only on thebank-shaped pattern 42. The bank-shaped pattern 42 is 10 μm in width.The overlapping margin of the bank-shaped pattern 42 and the pixelelectrode 15 is 4 μm.

Note that the characteristic of this embodiment is that the liquidcrystal orientation on the bank-shaped pattern 42 is made non-vertical.Therefore, other conditions such as the overlapping width with the edgeof the pixel electrode 15 are not restrictive of the present invention.

As explained above, according to this embodiment, the orientationabnormality within the pixel region for display caused by the slantingelectric field which occurs outside the pixel region for display and inits vicinity is suppressed and the liquid crystal orientation iscontrolled to be in a stable and ideal state. Thereby, irregular displayor ununiformity in display brightness is prevented from occurring andthe light transmittance of the panel is enhanced to a great extent. Thismakes it possible to realize a liquid crystal display device with highreliability.

Sixth Embodiment

The sixth embodiment of the present invention will be described below.Here, a liquid crystal display device based on the MVA system will bedescribed like in the fourth embodiment but the orientation controlprovided near the edge of the pixel electrode is performed in adifferent way.

Like in the first embodiment schematically shown in FIG. 1, this liquidcrystal display device is composed of a pair of transparent glasssubstrates 11, 12 facing each other with a predetermined spaced intervalbeing provided therebetween and the liquid crystal layer 13 interposedbetween the transparent glass substrates 11, 12. On the transparentglass substrate 11, the pixel electrodes 15, the data bus lines 21, thegate bus line (not shown), and so on are formed. On the transparentglass substrate 12, the color filter 17, the common electrode 18, and soon are formed.

In the liquid crystal display device, as shown in FIG. 19A, the slitpattern 23, which is the orientation control element extending in theoblique direction relative to the edge of the pixel electrode 15, isformed in the pixel electrode 15 on the surface of the transparent glasssubstrate 11 as the TFT substrate.

Incidentally, in this case, a bank-shaped pattern, which is a linearprotrusion, may be formed instead of the slit pattern 23 in the sameposition where the slit pattern 23 is formed.

Meanwhile, on the surface of the transparent glass substrate 12 as theCF substrate, the bank-shaped (linear protrusion) pattern 41, which isthe orientation control element extending in the oblique directionrelative to the edge of the pixel electrode 15 on the opposedtransparent glass substrate 11, is formed on the common electrode toextend substantially in parallel to the extending direction of the slitpattern 23. Thereby, predetermined division, for example, the fourdivided orientation, is performed on each pixel of the liquid crystallayer 13.

Moreover, on the surface of the transparent glass substrate 12, as shownin FIG. 19A and FIG. 19B (a sectional view taken along the I–I′ line), abank-shaped pattern (an auxiliary bank) 43, which is an assembly ofprotrusions having shapes with directivity along the edge of the pixelelectrode 15, a triangle-shaped section here, and being tapered towardan opposite side of the bank-shaped pattern 41, is integrally formedwith the bank-shaped pattern 41 to branch off in the oblique directionfrom the bank-shaped pattern 41.

Incidentally, in this case, slit patterns may be provided instead of thebank-shaped patterns 41, 43 in the same positions where the bank-shapedpatterns 41, 43 are formed.

Here, the direction of the directivity defined by the bank-shapedpattern 43 is the same as the orientation direction of the liquidcrystal molecules which causes the dark line to occur under voltageapplication, that is, a parallel direction to the extending direction ofthe bank-shaped pattern 43. Thereby, under voltage application, the darkline occurs stably only on the bank-shaped pattern 43 which has thedirectivity. Consequently, an actual adverse effect due to an occurrenceof the dark line is eliminated and an actually high light transmittanceof the panel can be realized.

[Specific Example of Structure]

The structure of this example is the same as the specific structure inthe fourth embodiment except in the following point.

As shown in FIGS. 19A and 19B, the bank-shaped pattern 43 which isdisposed along the edge of the pixel electrode 15 is shaped to have thedirectivity in a parallel direction to the substrate's plane surface. Anisosceles triangle-shaped section is used as the shape with thedirectivity. The base of the triangle is 5 μm and the height is 9 μm.The triangles (four in this embodiment) are arranged being connectedwith each other. An overlapping margin of the bank-shaped pattern 43 andthe pixel electrode 15 is 4 μm.

The bank-shaped pattern 43 having the directivity needs to be arrangedto have directivity toward an outer direction from the bank-shapedpattern 41 which extends in the direction of 45° relative to the edge ofthe adjacent pixel electrode 15. This arrangement makes it possible torealize orientation control by which the dark line is allowed to occurstably on the position of the bank-shaped pattern 43.

Note that the characteristic of this embodiment is that the bank-shapedpattern along the edge of the pixel electrode has the directivity.Therefore, other conditions such as the overlapping width with the edgeare not restrictive of the present invention.

Incidentally, as shown in FIG. 20A and FIG. 20B (a sectional view takenalong the line I–I′), the bank-shaped pattern 43 having the directivitymay be disposed not on the CF substrate but on the TFT substrate.Furthermore, it is also appropriate that the bank-shaped pattern 43 isdisposed on both of the substrates. In this case, the bank-shapedpattern 43 has a triangle-shaped section and in contrast to the case inFIG. 19A, is tapered toward the bank-shaped pattern 41.

Seventh Embodiment

The seventh embodiment of the present invention will be described below.Here, a liquid crystal display device based on the MVA system like inthe fourth embodiment will be described. But, an orientation controlprovided near the edge of the pixel electrode is performed in adifferent way.

Like in the first embodiment schematically shown in FIG. 1, this liquidcrystal display device is composed of a pair of transparent glasssubstrates 11, 12 facing each other with a predetermined spaced intervalbeing provided therebetween and the liquid crystal layer 13 interposedbetween the transparent glass substrates 11, 12. On the transparentglass substrate 11, the pixel electrodes 15, the data bus lines 21, thegate bus line (not shown), and so on are formed. On the transparentglass substrate 12, the color filter 17, the common electrode 18, and soon are formed.

In the liquid crystal display device, as shown in FIG. 21A, the slitpattern 23, which is the orientation control element extending in theoblique direction relative to the edge of the pixel electrode 15, isformed in the pixel electrode 15 on the surface of the transparent glasssubstrate 11 as the TFT substrate.

Incidentally, in this case, a bank-shaped pattern, which is a linearprotrusion, may be formed instead of the slit pattern 23 in the sameposition where the slit pattern 23 is formed.

Meanwhile, on the surface of the transparent glass substrate 12 as theCF substrate, the slit pattern 31, which is the orientation controlelement extending in the oblique direction relative to the edge of thepixel electrode 15 on the opposed transparent glass substrate 11, isformed in the common electrode to extend substantially in parallel tothe extending direction of the slit pattern 23. Thereby, predetermineddivision, for example, the four divided orientation, is performed oneach pixel of the liquid crystal layer 13.

Moreover, on the surface of the transparent glass substrate 12, the slitpattern 44 is integrally formed with the slit pattern 31 along the edgeof the pixel electrode 15 to branch off in the oblique direction fromthe slit pattern 31 as shown in FIG. 21A and FIG. 21B.

Incidentally, in this case, bank-shaped patterns, which are linearprotrusions, may be provided instead of the slit patterns 31, 44 in thesame positions where the slit patterns 31, 44 are formed.

Here, at least a part of the liquid crystal molecules of the liquidcrystal layer 13 on the slit pattern 44 are vertically oriented whenvoltage is being applied between the pixel electrode 15 and the commonelectrode 18. Specifically, no pixel electrode 15 exists at least on apart of a place facing the slit pattern 44 on the CF substrate.

One of the causes which strengthen the slanting electric field of thepixel electrode 15, which is one factor of causing unevenness among eachshot at the time of patterning, is an influence from an electric fieldof an adjacent data bus line. In this embodiment, a region in which theliquid crystal orientation does not change (remains in the verticaldirection) is provided between the data bus line 21 and the pixelelectrode 15 so that the influence given to the liquid crystalorientation on the pixel electrode 15 by the bus line can be eliminated.As a result, the slanting electric field of the edge of the pixelelectrode 15 can be weakened and the unevenness among each shot can beprevented from occurring.

[Specific Example of Structure]

The structure of this example is the same as the specific structure inthe fourth embodiment except in the following point.

As shown in FIGS. 21A and 21B, the slit pattern 31, which is disposed toextend in the direction of 45° relative to the edge of the pixelelectrode 15, and the slit pattern 44, which is disposed to extend alongthe edge of the pixel electrode 15, are both 10 μm in width and anoverlapping width of the data bus line 21 and the slit pattern 44 is 2μm.

The distance between the pixel electrode 15 and the adjacent data busline 21 is 10 μm. This means that a region of 8 μm with no electrodeexists between the pixel electrode 15 and the data bus line 21.Consequently, with no electrode existing in the region, the liquidcrystal molecules maintain their vertical orientation state in thisregion even when voltage is being applied to the electrodes in theirvicinity.

Moreover, when an insulating film is selectively formed in the regionwithout any electrode existing therein, thickness of a cell in thisregion is made thinner than that in other regions. Thereby, the verticalorientation state can be more stably realized.

Note that the characteristic of this embodiment is that the liquidcrystal molecules between the pixel electrode and the bus line aremaintained in the vertical orientation state under voltage application.Therefore, other conditions such as an overlapping width with the pixeledge is not restrictive of this invention.

As explained above, according to this embodiment, the orientationabnormality within the pixel region for display caused by the slantingelectric field which occurs outside the pixel region for display and inits vicinity is suppressed and the liquid crystal orientation iscontrolled to be in a stable and ideal state. Thereby, irregular displayor ununiformity in display brightness is prevented from occurring andthe light transmittance of the panel is greatly enhanced. This makes itpossible to realize a liquid crystal display device with highreliability.

According to the present invention, the orientation abnormality withinthe pixel region for display caused by the slanting electric field whichoccurs outside the pixel region for display and in its vicinity issuppressed and the liquid crystal orientation is controlled to be in astable and ideal state. Thereby, irregular display or ununiformity indisplay brightness is prevented from occurring and the lighttransmittance of the panel is greatly enhanced. This makes it possibleto realize a liquid crystal display device with high reliability.

1. A liquid crystal display device comprising: a first substrate having thereon a pixel electrode and an active element; a second substrate having thereon an opposed electrode; a liquid crystal layer interposed between said first and second substrates with said electrodes facing each other; and a first orientation control element extending in a nonparallel direction relative to an extending direction of an edge of said pixel electrode, and a second orientation control element extending from said first orientation element in a parallel direction relative to an extending direction of said edge provided on at least one of said first and second substrates; wherein said second orientation control element has a constant width, and said width is smaller than a width of said first orientation control element.
 2. The device according to claim 1, wherein at least one of said first and second orientation control elements is a slit formed in said pixel electrode or said opposed electrode.
 3. The device according to claim 1, wherein at least one of said first and second orientation control elements is a protrusion formed on said pixel electrode or said opposed electrode.
 4. The device according to claim 1, wherein a dielectric anisotropy of liquid crystal molecules of said liquid crystal layer is negative. 